Sulfur-containing, compounds, nitrogen-containing compounds, oxygen-containing compounds, and the like are contained in crude oil as impurities, and these impurities are also contained in petroleum fractions obtained by fractionating the crude oil. For the above impurities in these petroleum fractions, reducing their content is performed by the step of contacting with a catalyst having hydrotreating activity in the presence of hydrogen, called hydrotreating. Particularly, desulfurization in which the content of sulfur-containing compounds is reduced is well known. Recently, in terms of the reduction of environmental loads, a demand for the restriction and reduction of the content of the above impurities, including sulfur-containing compounds, in petroleum products, has become stricter, and many so-called “sulfur-free” petroleum products have been produced.
When a hydrotreating catalyst used for the hydrotreatment of petroleum fractions described above is used for a certain period, activity decreases due to the deposition of coke and sulfur components, and the like, and therefore, replacement is performed. Particularly, the above “sulfur-free” is required, and high hydrotreating ability is required in facilities for the hydrotreatment of fractions, such as kerosene, light oil, and reduced pressure light oil. As a result, catalyst replacement frequency increases, which, as a result, leads to an increase in catalyst cost and an increase in the amount of the catalyst discarded.
As measures for this, the use of a regenerated catalyst for which a spent hydrotreating catalyst is regenerated (regenerated hydrotreating catalyst) is partly performed in these facilities (for example, see Patent Literatures 1 and 2).